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This thesis is concerned with analytical studies on the trace analytes barium, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, vanadium and zinc, present in high purity and highly complex matrices. The technique utilises activated alumina microcolumns in a flow injection (FI) system, to perform analyte enrichment and matrix removal. The analytes, after retention on the microcolumn are subsequently eluted and quantified by inductively coupled plasma-emission spectrometry (ICP-ES).Initial studies focus on trace analytes in caesium iodide, however a selection of the alkali metal salts, lithium nitrate, potassium bromide, sodium fluoride and sodium chloride, are investigated. New methodology for the ultratrace determination of high purity alkali metal salts is thus provided. The microcolumn enrichment technique with ICP-ES detection is robust, utilises limited sample handling and simultaneously preconcentrates and separates the analytes from matrix components. Hence possible matrix interferences are eliminated and limits of detection are significantly improved, in comparison to conventional ICP-ES analysis. A technique for the determination of the total content of eleven trace analytes present in natural waters (mineral, reservoir), using microcolumns of activated alumina in a FI-ICP-ES is investigated. The use of the complexing agent tartaric acid is shown to be effective in improving analyte retention. The procedure is successfully applied to determination of these analytes in a certified river water reference material (SLRS-1). Due to low retention and elution efficiencies, the total content of the analytes Fe and V present in Buxton, Redmires and Langsett samples could not be accurately determined by this technique. Activated alumina microcolumns are utilised as a new field sampling tools. Samples are collected in the field and processed through the alumina microcolumns for the effective retention of desired analytes. Hence, an alumina microcolumn sampling stage to effect concentration and isolation prior to analytical measurement is at the core of the investigation. The overall aim is to extend the application of alumina microcolumns, and in particular to provide a new multi-element field sampling device, which gives high sample integrity and preconcentration.

Silicon dispersions in water are used to produce pyrotechnic time delay compositions employed in mine detonators. The delay elements are manufactured by pressing the pyrotechnic composition into aluminium tubes. The automated filling and pressing process requires powders with good free-flow behaviour. Spray drying of water-based slurries is an appropriate method for obtaining such free-flowing granules as it creates almost perfectly spherical particle agglomerates. In addition to the acceptable flow properties, this process provides well-mixed compositions at desired particle size distributions. However, a potential hazard situation arises when water reacts dissociatively with silicon to form SiO2 and hydrogen gas according to Si + 2H2O _ SiO2 + 2H2↑. The propensity of the silicon to react with water and to release hazardous hydrogen gas must thus be suppressed. To this end, the following methods were investigated as a means of diminishing the rate of hydrogen evolution: (i) controlling the slurry pH; (ii) adding organic corrosion inhibitors; (iii) controlled silicon air oxidation before slurrying; and (iv) adding suitable metal ions to provide an additional cathodic reaction to that of water. The effect of organic surface modifications and medium pH on the rate of corrosion of silicon was studied at ambient temperature. It was found that the rate of hydrogen evolution increased with increasing pH. Silanes proved to be more effective silicon corrosion inhibitors than alcohols, with vinyl tris(2-methoxyethoxy) silane producing the best results from the silanes investigated. Differential thermal analysis (DTA) studies were performed using a near-stoichiometric amount of lead chromate as oxidant. Comparable combustion behaviour was observed when both the fuel and the oxidant powders were either uncoated or silane modified. Mixtures of neat oxidant with silane-coated silicon showed poor burn behaviour and this was attributed to poor particle- particle mixing due to the mismatch in surface energies. The controlled silicon air oxidation results showed that the best hydrogen evolution inhibition was attained upon formation of a SiO2 passivating layer at 350 °C. However, Fourier transform infrared (FTIR) data also suggest that some inhibition was imparted below 350 °C and this is due mainly to the removal of silicon surface hydroxyl groups rather than an increase in the SiO2 thickness. DTA studies performed using a nearstoichiometric amount of lead chromate revealed that although heat treatment at higher temperatures provides better passivation; it reduces the reactivity of the silicon in pyrotechnic compositions. The ignition temperature increases while the energy output decreases. Water oxidises silicon via an electrochemical reaction that produces hydrogen gas. The last approach considered in this study was the introduction of a competing cathodic reaction as a means of suppressing the liberation of hydrogen. It was found that the addition of metal ions with a higher reduction potential than hydrogen ions, e.g. copper (II) ions, reduced the amount of hydrogen liberated. In the presence of copper ions the reaction with water featured three distinct stages. During the initial stage, copper is deposited on the silicon and a rapid drop in solution pH is observed. Most of the hydrogen evolved during a second active stage, with the pH showing a slight upward drift. Finally, in the third stage, hydrogen evolution stopped as the silicon surface became passive. The reduction in the total hydrogen evolved was attributed to copper deposits reducing the active surface area available for the oxidation of silicon and to the presence of copper which facilitates accelerated passivation of the uncoated silicon surface. The nature of the anions present affected both the amount of copper deposited on the silicon and the amount of hydrogen released. DTA studies showed that exposure of silicon to copper metal salt solutions also decreases the reactivity of the silicon fuel in pyrotechnic compositions. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Adverse reactions to metals is relatively frequent in sensitive individuals, and may lead to the development of various diseases, such as lichen planus and lichenoid reaction and was also described effect of amalgam to the pathology of autoimmune diseases. In sensitive patients with known reactions to metals leads to atrophy of the oral mucosa and discomfort (burning, cutting, excessive salivation). Adverse effects of dental materials are described as an allergic reaction type IV delayed hypersensitivity. It disrupt the immune system, increased vascular permeability, tissue is often damaged by chronic inflammation and it is also activated antigen- nonspecific component of immunity. Monocytes are the key cells of the immune system, which act as antigen presenting cells, in particular after conversion in the tissues into macrophages are directly involved in the activation of immune responses and their stimulation is therefore crucial for the development of adverse reactions to dental materials. In the thesis was measured cytokine production by monocytes after stimulation with metal salts. To determine the extent of the patients' responses to the metals was used lymphocyte proliferation assay (MELISA® ), which was developed and patented in Sweden. We compared lymphocyte proliferation after stimulation...

The effect of engineered nanoparticles (ENPs) mixture consisting of silver oxide, (Agg0[Silver Oxide Nanopartical], 20 nm), titanium dioxide, (TiO2[Titanium dioxide], 30-40 nm) and zinc oxide, (ZnO, 20 nm) compared with their bulk metal salts was evaluated against unspiked activated sludge (control) using 3 parallel pilot-scale treatment plants. The total concentration of the ionic species of Ag+ Ti[Silver + Titanium] and Zn(2+) in the effluent of the ENP spiked activated sludge (AS) was below limits of detection and> 99% of the spiked ENP were found in the waste activated sludge (WAS), whereas 39 – 58 % of Ag0[Silver Oxide Nanopartical], 51 – 63 % and 58 – 74 % of ZnO ion concentrations were recovered in the anaerobic digestate (AD) cake suggesting higher affinity of ENPs to WAS than to anaerobic digestate. ENPs induced a 2-fold increase of the microbial community specific oxygen uptake rate (SOUR) compared with the control and > 98 % of ammonia and 80 % of COD were removed from the AS suggesting that the heterotrophic biomass retained their ability to nitrify and degrade organic matter at the spiked ENP concentration. The floc size and cultivable microbial abundance was reduced in the ENP spiked AS with no apparent disruption of the overall AS process efficiency. However, scanning electron microscopic analysis clearly showed damage to specific microbial cells. The lipid fingerprint and 16S rRNA gene-based pyrosequencing evidenced the dominance of Proteobacteria, Firmicutes, and Bacteriodetes with a clear temporal shift in microbial community structure. The prominent nano-tolerant bacterial species identified were Acidovorax, Rhodoferax, and Comamonas whereas Methanocorpusculum and Methanosarcina were recovered in AS and were the dominant Archaea in the AD with 99 and 98 % similarities to the closest culturable relative. Their presence in the AS suggests tolerance to ENPs and oxygen-dependent respiration. V. fisheri activity was not sensitive to the ionic concentrations of the ENP or metal salt mixture in the digestate samples and illustrates the need to develop bioassay using indigenous wastewater microorganisms to detect the potential effect of ENP. Overall, unlike other xenobiotic compounds, ENPs can hasten the natural selection of microbial species in activated sludge and anaerobic digestion processes.

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Les nanocomposites constitués de nanoparticules métalliques finement dispersées dans une matrice isolante suscitent un grand intérêt en raison de leurs propriétés optiques, électriques ou antibactériennes permettant une variété d'applications technologiques. Dans ce travail, nous nous intéressons aux composites hybrides à base d’ une matrice polymère élaborée par polymérisation par plasma froid (PECVD), imprégnée par la suite avec une solution de sel métallique qui est finalement réduit. Ces nanocomposites sont essentiellement étudiés pour leurs applications et peu d’ études portent sur leur structure chimique et morphologique.Dans ce travail de thèse, notre objectif est ainsi d’ étudier la dépendance des propriétés chimiques et morphologiques de tels matériaux composites vis-à-vis de la structure chimique du polymère plasma, de la nature des nanoparticules métalliques et des fonctions chimiques du polymère impliquées dans les interactions polymère / métal. La matrice sera aussi bien un polymère plasma qu’ un mélange de deux polymères plasma. L'objectif est alors de mieux comprendre la formation de ces nanocomposites, et de montrer leur intérêt dans différentes applications et notamment la détection d'ammoniac. / Nanocomposites consisting of finely dispersed metal nanoparticles into insulating matrix are the focus of much attention because of their optical, electrical or antibacterial properties, allowing a variety of technological applications. In this work, we are interested in hybrid composites based on a polymer matrix synthesized by cold plasma polymerization (PECVD), subsequently impregnated with a solution of metal salt which is finally reduced. These nanocomposites are mainly studied for their applications and less focused on their chemical and morphological structure. In this work, our goal is to study the dependence of chemical and morphological properties of such composite materials on the chemical structure of the plasma polymer, the nature of the metal nanoparticles and the chemical functions of the polymer involved with the polymer / metal interactions. The matrix will be both a plasma polymer and a mixture of two plasma polymers. The objective is then to better understand the nanocomposites formation, and to show their interest in different applications particularly in the detection of ammonia gas.